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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

What is stdClass in PHP?

Please define what stdClass is.

PHP and Enumerations

I know that PHP doesn't have native Enumerations. But I have become accustomed to them from the Java world. I would love to use enums as a way to give predefined values which IDEs' auto completion features could understand.

Constants do the trick, but there's the namespace collision problem and (or actually because) they're global. Arrays don't have the namespace problem, but they're too vague, they can be overwritten at runtime and IDEs rarely (never?) know how to autofill their keys.

Are there any solutions/workarounds you commonly use? Does anyone recall whether the PHP guys have had any thoughts or decisions around enums?

What's the best method for sanitizing user input with PHP?

Is there a catchall function somewhere that works well for sanitizing user input for SQL injection and XSS attacks, while still allowing certain types of html tags?

UTF-8 all the way through

I'm setting up a new server, and want to support UTF-8 fully in my web application. I have tried in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.

Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL and PHP to do this - is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur?

This is for a new Linux server, running MySQL 5, PHP 5 and Apache 2.

When to use self over $this?

In PHP 5, what is the difference between using self and $this?

When is each appropriate?

Why shouldn't I use mysql_* functions in PHP?

What are the technical reasons why I shouldn't use mysql_* functions? (e.g. mysql_query(), mysql_connect() or mysql_real_escape_string())?

Why should I use something else even if they work on my site?

How to get the client IP address in PHP?

How can I get the client IP address using PHP?

I want to keep record of the user who logged into my website through his/her IP address.