Creating them, joining them, and the functions you’ll use most often.
Understanding strings in PHP
A string is a sequence of characters. In PHP each character is one byte, so the language works with a 256-character set rather than full native Unicode.
Creating strings
Wrap text in single quotes (') or double quotes ("):
<?php
$singleQuoted = 'Hello, PHP!';
$doubleQuoted = "Hello, PHP!";
?>Concatenating strings
Concatenation means joining strings together. In PHP you use the dot (.) operator:
<?php
$firstPart = "Hello, ";
$secondPart = "world!";
$combinedString = $firstPart . $secondPart;
echo $combinedString; // Outputs 'Hello, world!'
?>Single vs double quotes
It matters which quotes you pick. Double-quoted strings expand variables and some escape sequences. Single-quoted strings treat almost everything literally.
<?php
$name = "Alice";
echo "Hello, $name!"; // Outputs 'Hello, Alice!'
echo 'Hello, $name!'; // Outputs 'Hello, $name!'
?>Common string functions
PHP ships with plenty of string helpers. These come up often:
strlen()
Returns the length of a string.
<?php
echo strlen("Hello, PHP!"); // Outputs 11
?>str_word_count()
Counts the words in a string.
<?php
echo str_word_count("Hello, world!"); // Outputs 2
?>strrev()
Reverses a string.
<?php
echo strrev("Hello, PHP!"); // Outputs '!PHP ,olleH'
?>strpos()
Finds the position of the first occurrence of a substring.
<?php
echo strpos("Hello, world!", "world"); // Outputs 7
?>str_replace()
Replaces one substring with another.
<?php
echo str_replace("world", "PHP", "Hello, world!"); // Outputs 'Hello, PHP!'
?>String formatting
When you need tidy, predictable output, these two are useful:
sprintf()
Formats a string to a specific layout.
<?php
$number = 9;
$formattedString = sprintf("The number is %02d", $number);
echo $formattedString; // Outputs 'The number is 09'
?>number_format()
Formats a number with grouped thousands.
<?php
echo number_format("1000000"); // Outputs '1,000,000'
?>Working with substrings
Sometimes you only need part of a string. PHP has a few functions for that:
substr()
Returns part of a string.
<?php
echo substr("Hello, world!", 7, 5); // Outputs 'world'
?>strstr()
Finds the first occurrence of a string inside another string.
<?php
echo strstr("hello@example.com", "@"); // Outputs '@example.com'
?>Practical example: email extraction
Split an email address into username and domain:
<?php
$email = "user@example.com";
$domain = strstr($email, '@');
$username = strstr($email, '@', true);
echo "Domain: $domain<br>";
echo "Username: $username<br>";
?>Most PHP pages spend a fair bit of time shuffling strings around – output, form data, database values. These functions cover the everyday cases.