smallseo.info

startsWith() and endsWith() functions in PHP

How can I write two functions that would take a string and return if it starts with the specified character/string or ends with it?

For example:

$str = '|apples}';

echo startsWith($str, '|'); //Returns true
echo endsWith($str, '}'); //Returns true

How can I prevent SQL-injection in PHP?

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to SQL injection, like in the following example:

$unsafe_variable = $_POST['user_input']; 

mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");

That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:

INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')

What can be done to prevent this from happening?

Reference - What does this symbol mean in PHP?

What is this?

This is a collection of questions that come up every now and then about syntax in PHP. This is also a Community Wiki, so everyone is invited to participate in maintaining this list.

Why is this?

It used to be hard to find questions about operators and other syntax tokens.¹
The main idea is to have links to existing questions on Stack Overflow, so it's easier for us to reference them, not to copy over content from the PHP Manual.

¹ Note: Since January 2013, Stack Overflow does support special characters. Just surround the search terms by quotes, e.g. [php] "==" vs "==="

What should I do here?

If you have been pointed here by someone because you have asked such a question, please find the particular syntax below. The linked pages to the PHP manual along with the linked questions will likely answer your question then. If so, you are encouraged to upvote the answer. This list is not meant as a substitute to the help others provided.

The List

If your particular token is not listed below, you might find it in the List of Parser Tokens.

& Bitwise Operators or References

• What does it mean to start a PHP function with an ampersand?
• Understanding PHP & (ampersand, bitwise and) operator
• PHP "&" operator
• difference between & and && in PHP
• What does "&" mean here in PHP?
• what does & mean in this case?
• What does the & sign mean in PHP?
• What does this signature mean(&) in PHP?
• How does "&" operator work in PHP function?
• What does & in &2 mean in PHP?
• When should I use Bitwise operator?
• Is there ever a need to use ampersand in front of an object

=& References

• Reference assignment operator in php =&
• what do "=&" / "&=" operators in php mean?
• What do the '&=' and '=&' operators do?
• What does =& mean in PHP?

&= Bitwise Operators

• what do "=&" / "&=" operators in php mean?
• What do the '&=' and '=&' operators do?

&& Logical Operators

• 'AND' vs '&&' as operator
• difference between & and && in PHP
• PHP: Is there a difference between operators AND and && here?
• PHP - and / or keywords

% Arithmetic Operators

• What does the percent sign mean in PHP?
• What is the PHP operator % and how to use it in real world examples?

!! Logical Operators

• Double Not (!!) Operator in PHP

@ Error Control Operators

• What is the use of @ symbol in php?
• PHP - 'At' symbol before variable name: @$_POST
• PHP functions and @functions
• Should I use @ in my PHP code?

?: Ternary Operator

• What is ?: in PHP 5.3?
• What is the PHP ? : operator called and what does it do?
• ?: operator (the 'Elvis operator') in PHP
• Where can I read about conditionals done with ? and :
• Using PHP 5.3 ?: operator

?? Null Coalesce Operator (since PHP 7)

• C#'s null coalescing operator (??) in PHP?

: Alternative syntax for control structures, Ternary Operator

• What is this : in php?
• What does this ":" mean in PHP?

:: Scope Resolution Operator

• What do two colons mean in PHP?
• What's the meaning of the PHP Token Name T_PAAMAYIM_NEKUDOTAYIM
• What's the difference between :: (double colon) and -> (arrow) in PHP?
• What exactly are late static bindings in PHP?
• static::staticFunctionName()
• Unexpected T_PAAMAYIM_NEKUDOTAYIM, expecting T_NS_Separator

\ Namespaces

• Backslash in PHP -- what does it mean?
• What does a \ (backslash) do in PHP (5.3+)?

-> Classes And Objects

• What is the "->" PHP operator called and how do you say it when reading code out loud?
• where we use object operator "->" in php
• What's the difference between :: (double colon) and -> (arrow) in PHP?
• What does this PHP syntax mean: $var1->$var2
• Absolutely basic PHP question about the "-> " syntax

=> Arrays

• What does "=>" mean in PHP?
• Use of => in PHP
• What does $k => $v in foreach($ex as $k=>$v) mean?

^ Bitwise Operators

• How does the bitwise operator XOR ('^') work?
• What does ^ mean in PHP?

>> Bitwise Operators

• What does >> mean in PHP?

<< Bitwise Operators

• Strange print behaviour in PHP?

<<< Heredoc or Nowdoc

• What does <<<END mean in PHP?
• PHP <<<EOB
• In PHP, what does "<<<" represent?
• Using <<<CON in PHP
• What's this kind of syntax in PHP?

= Assignment Operators

• The 3 different equals

== Comparison Operators

• php == vs === operator
• How do the PHP equality (== double equals) and identity (=== triple equals) comparison operators differ?
• PHP != and == operators
• The 3 different equals
• PHP Type-Juggling and (strict) Greater/Lesser Than Comparisons

=== Comparison Operators

• What does "===" mean?
• php == vs === operator
• How do the PHP equality (== double equals) and identity (=== triple equals) comparison operators differ?
• The 3 different equals
• PHP Type-Juggling and (strict) Greater/Lesser Than Comparisons

!== Comparison Operators

• What does !== comparison operator in PHP mean?
• Is there a difference between !== and != in PHP?

!= Comparison Operators

• PHP != and == operators
• Is there a difference between !== and != in PHP?
• comparing, !== versus !=
• What is the difference between <> and !=

<> Comparison Operators

• php operator <>
• php <> operator
• What is the difference between <> and !=
• PHP Type-Juggling and (strict) Greater/Lesser Than Comparisons

<=> Comparison Operators (since PHP 7.0)

• Spaceship (three way comparison) operator

| Bitwise Operators

• What is the difference between the | and || operators?
• What Does Using A Single Pipe '|' In A Function Argument Do?

|| Logical Operators

• What is the difference between the | and || operators?
• PHP - and / or keywords
• What exactly does || mean?
• The behaviour of the or operator in PHP

~ Bitwise Operators

• What does this ~ operator mean here?

+ Arithmetic Operators, Array Operators

• + operator for array in PHP?

+= Assignment Operators

• What is += used for?
• What does `$page -= 1` in my PHP document mean?

++ Incrementing/Decrementing Operators

• Understanding Incrementing
• Answer below

.= Assignment Operators

• What is the difference between .= and += in php
• To understand a line of PHP

. String Operators

• Difference between "," and "." in PHP?
• What does a . (dot) do in PHP?

, Function Arguments

• Difference between "," and "." in PHP?

$$ Variable Variables

• What does $$ mean in PHP?
• what is "$$" in PHP
• $function() and $$variable

` Execution Operator

• What are the backticks `` called?

<?= Short Open Tags

• What does this symbol mean in PHP <?=
• What does '<?=' mean in PHP?
• What does <?= mean?

[] Arrays

• PHP arrays... What is/are the meaning(s) of an empty bracket?
• PHP : What is the meaning of []
• Php array_push() vs myArray[]
• What does [] mean when reading from a php array?
• Shorthand for arrays: literal $var = [] empty array

<? Opening and Closing tags

• Are PHP short tags acceptable to use?

... Argument unpacking (since PHP 5.6)

** Exponentiation (since PHP 5.6)

# One-line shell-style comment

• What does # mean in PHP?
• Can I use hashes for comments in PHP?

Check if string contains specific words?

Consider:

$a = 'How are you?';

if ($a contains 'are')
    echo 'true';

Suppose I have the code above, what is the correct way to write the statement if ($a contains 'are')?

Using a regular expression to validate an email address

Over the years I have slowly developed a regular expression that validates MOST email addresses correctly, assuming they don't use an IP address as the server part.

I use it in several PHP programs, and it works most of the time. However, from time to time I get contacted by someone that is having trouble with a site that uses it, and I end up having to make some adjustment (most recently I realized that I wasn't allowing 4-character TLDs).

What's the best regular expression you have or have seen for validating emails?

I've seen several solutions that use functions that use several shorter expressions, but I'd rather have one long complex expression in a simple function instead of several short expression in a more complex function.

How do you use bcrypt for hashing passwords in PHP?

Every now and then I hear the advice "Use bcrypt for storing passwords in PHP, bcrypt rules".

But what is bcrypt? PHP doesn't offer any such functions, Wikipedia babbles about a file-encryption utility and Web searches just reveal a few implementations of Blowfish in different languages. Now Blowfish is also available in PHP via mcrypt, but how does that help with storing passwords? Blowfish is a general purpose cipher, it works two ways. If it could be encrypted, it can be decrypted. Passwords need a one-way hashing function.

What is the explanation?

Convert HTML + CSS to PDF with PHP?

Ok, I'm now banging my head against a brick wall with this one.

I have an HTML (not XHTML) document that renders fine in Firefox 3 and IE 7. It uses fairly basic CSS to style it and renders fine in HTML.

I'm now after a way of converting it to PDF. I have tried:

• DOMPDF: it had huge problems with tables. I factored out my large nested tables and it helped (before it was just consuming up to 128M of memory then dying--thats my limit on memory in php.ini) but it makes a complete mess of tables and doesn't seem to get images. The tables were just basic stuff with some border styles to add some lines at various points;
• HTML2PDF and HTML2PS: I actually had better luck with this. It rendered some of the images (all the images are Google Chart URLs) and the table formatting was much better but it seemed to have some complexity problem I haven't figured out yet and kept dying with unknown node_type() errors. Not sure where to go from here; and
• Htmldoc: this seems to work fine on basic HTML but has almost no support for CSS whatsoever so you have to do everything in HTML (I didn't realize it was still 2001 in Htmldoc-land...) so it's useless to me.

I tried a Windows app called Html2Pdf Pilot that actually did a pretty decent job but I need something that at a minimum runs on Linux and ideally runs on-demand via PHP on the Webserver.

I really can't believe I'm this stuck. Am I missing something?

How do you parse and process HTML/XML in PHP?

How can one parse HTML/XML and extract information from it?

This is a General Reference question for the php tag

How to fix "Headers already sent" error in PHP

When running my script, I am getting several errors like this:

Warning: Cannot modify header information - headers already sent by (output started at /some/file.php:12) in /some/file.php on line 23

The lines mentioned in the error messages contain header() and setcookie() calls.

What could be the reason for this? And how to fix it?

How does 'foreach' actually work?

Let me prefix this by saying that I know what foreach is, does and how to use it. This question concerns how it works under the bonnet, and I don't want any answers along the lines of "this is how you loop an array with foreach".

For a long time I assumed that foreach worked with the array itself. Then I found many references to the fact that it works with a copy of the array, and I have since assumed this to be the end of the story. But I recently got into a discussion on the matter, and after a little experimentation found that this was not in fact 100% true.

Let me show what I mean. For the following test cases, we will be working with the following array:

$array = array(1, 2, 3, 4, 5);

Test case 1:

foreach ($array as $item) {
  echo "$item\n";
  $array[] = $item;
}
print_r($array);

/* Output in loop:    1 2 3 4 5
   $array after loop: 1 2 3 4 5 1 2 3 4 5 */

This clearly shows that we are not working directly with the source array - otherwise the loop would continue forever, since we are constantly pushing items onto the array during the loop. But just to be sure this is the case:

Test case 2:

foreach ($array as $key => $item) {
  $array[$key + 1] = $item + 2;
  echo "$item\n";
}

print_r($array);

/* Output in loop:    1 2 3 4 5
   $array after loop: 1 3 4 5 6 7 */

This backs up our initial conclusion, we are working with a copy of the source array during the loop, otherwise we would see the modified values during the loop. But...

If we look in the manual, we find this statement:

When foreach first starts executing, the internal array pointer is automatically reset to the first element of the array.

Right... this seems to suggest that foreach relies on the array pointer of the source array. But we've just proved that we're not working with the source array, right? Well, not entirely.

Test case 3:

// Move the array pointer on one to make sure it doesn't affect the loop
var_dump(each($array));

foreach ($array as $item) {
  echo "$item\n";
}

var_dump(each($array));

/* Output
  array(4) {
    [1]=>
    int(1)
    ["value"]=>
    int(1)
    [0]=>
    int(0)
    ["key"]=>
    int(0)
  }
  1
  2
  3
  4
  5
  bool(false)
*/

So, despite the fact that we are not working directly with the source array, we are working directly with the source array pointer - the fact that the pointer is at the end of the array at the end of the loop shows this. Except this can't be true - if it was, then test case 1 would loop forever.

The PHP manual also states:

As foreach relies on the internal array pointer changing it within the loop may lead to unexpected behavior.

Well, let's find out what that "unexpected behavior" is (technically, any behavior is unexpected since I no longer know what to expect).

Test case 4:

foreach ($array as $key => $item) {
  echo "$item\n";
  each($array);
}

/* Output: 1 2 3 4 5 */

Test case 5:

foreach ($array as $key => $item) {
  echo "$item\n";
  reset($array);
}

/* Output: 1 2 3 4 5 */

...nothing that unexpected there, in fact it seems to support the "copy of source" theory.

The Question

What is going on here? My C-fu is not good enough for me to able to extract a proper conclusion simply by looking at the PHP source code, I would appreciate it if someone could translate it into English for me.

It seems to me that foreach works with a copy of the array, but sets the array pointer of the source array to the end of the array after the loop.

• Is this correct and the whole story?
• If not, what is it really doing?
• Is there any situation where using functions that adjust the array pointer (each(), reset() et al.) during a foreach could affect the outcome of the loop?

Delete an element from an array

Is there an easy way to delete an element from a PHP array, such that foreach ($array) no longer includes that element?

I thought that setting it to null would do it, but apparently not.

How do I get a YouTube video thumbnail from the YouTube API?

If I have a YouTube video URL, is there any way to use PHP and cURL to get the associated thumbnail from the YouTube API?

PHP detecting request type (GET, POST, PUT or DELETE)

How can I detect which request type was used(GET, POST, PUT or DELETE) in php?

Sort Multi-dimensional Array by Value [duplicate]

Possible Duplicate:
How do I Sort a Multidimensional Array in PHP

How can I sort this array by the value of the "order" key? Even though the values are currently sequential, they will not always be.

Array
(
    [0] => Array
        (
            [hashtag] => a7e87329b5eab8578f4f1098a152d6f4
            [title] => Flower
            [order] => 3
        )

    [1] => Array
        (
            [hashtag] => b24ce0cd392a5b0b8dedc66c25213594
            [title] => Free
            [order] => 2
        )

    [2] => Array
        (
            [hashtag] => e7d31fc0602fb2ede144d18cdffd816b
            [title] => Ready
            [order] => 1
        )
)

I never really understood: what is CGI?

CGI is a Common Gateway Interface. As the name says, it is a "common" gateway interface for everything. It is so trivial and naive from the name. I feel that I understood this and I felt this every time I encountered this word. But frankly, I didn't. I'm still confused.

I am a PHP programmer. I did lot of web development.

user (client) request for page ---> webserver(->embedded PHP interpreter) ----> Server side(PHP) Script ---> MySQL Server.

Now say my PHP Script can fetch results from MySQL Server && MATLAB Server && Some other server.

So, now PHP Script is the CGI? because its interface for the between webserver & All other servers? I don't know. Sometimes they call CGI, a technology & othertimes they call CGI a program or someother server.

• What exactly is CGI?

• Whats the big deal with /cgi-bin/*.cgi? What's up with this? I don't know what is this cgi-bin directory on the server for. I don't know why they have *.cgi extensions.

• Why does Perl always comes in the way. CGI & Perl (language). I also don't know what's up with these two. Almost all the time I keep hearing these two in combination "CGI & Perl". This book is another great example CGI Programming with Perl. Why not "CGI Programming with PHP/JSP/ASP"? I never saw such things.

• CGI Programming in C, confuses me a lot. "in C"?? Seriously?? I don't know what to say. I'm just confused. "in C"?? This changes everything. Program needs to be compiled and executed. This entirely changes my view of web programming. When do I compile? How does the program gets executed (because it will be a machine code, so it must execute as a independent process). How does it communicate with the web server? IPC? and interfacing with all the servers (in my example MATLAB & MySQL) using socket programming? I'm lost!!

• They say that CGI is depreciated. Its no more in use. Is it so? What is its latest update?

Once, I ran into a situation where I had to give HTTP PUT request access to web server (Apache HTTPD). Its a long back. So, as far as I remember this is what I did:

1. Edited the configuration file of Apache HTTPD to tell webserver to pass all HTTP PUT requests to some put.php ( I had to write this PHP script)

2. Implement put.php to handle the request (save the file to the location mentioned)

People said that I wrote a CGI Script. Seriously, I didn't have a clue what they were talking about.

• Did I really write CGI Script?

I hope you understood what my confusion is. (Because I myself don't know where I'm confused). I request you guys to keep your answer as simple as possible. I really can't understand any fancy technical terminology. At least not in this case.

EDIT:

I found this amazing tutorial "CGI Programming Is Simple!" - CGI Tutorial, which explains the concepts in simplest possible way. After reading this article you may want to read Getting Started with CGI Programming in C to supplement your understanding with actual code samples. I've also added these links to this tutorial to Wikipedia's article : http://en.wikipedia.org/wiki/Common_Gateway_Interface