Strings

String is a sequence of symbols. All of the symbols can be accessed via their indexes starting from 0.

Indexes

Let's say we have the string "computer". It's structure is the following:

So if we need to print the first letter (c) and the 3rd letter (m), we do:

<?php $word = "computer"; echo $word[0] . $word[2];

Output:

cm

Length

Length is the count of the symbols contained in a string.

It's accessed via the strlen function.

Example:

<?php $word = "Hello!"; echo strlen($word);

Output:

6

Via strlen we can access the last symbol of a string.

Example:

<?php $str = "The quick brown fox jumps over the lazy dog!"; echo $str[strlen($str) - 1];

Output:

!

Access outside of bounds

Accessing string outside of it's bounds results in warning.

Let's look the following example:

<?php $str = "Phone"; $str[5];

The string has indexes from 0 to 4. Accessing index outside of that bound (in this case 5) causes warning.

Contains

We can check if string is contained in a string via the strpos function.

Examples:

<?php $str = "simple"; if(strpos($str, "m") !== false) { echo $str . ' contains m'; echo '<br>'; // Prints new line. } if(strpos($str, "si") !== false) { echo $str . ' contains si'; echo '<br>'; // Prints new line. } if(strpos($str, "z") !== false) { echo $str . ' contains z'; echo '<br>'; // Prints new line. } if(strpos($str, "S") === false) { echo $str . ' does not contain S'; echo '<br>'; // Prints new line. }

Output:

simple contains m simple contains si simple does not contain S

Note: you could use str_contains instead of strpos for PHP 8.0 and newer versions.

String iteration

All symbols of a string can be iterated via for loop.

Let's print all letters of a word that are not vowels:

<?php $word = "composure"; $vowels = "aeiou"; for ($i = 0; $i < strlen($word); $i++) { $letter = $word[$i]; // if $letter is not contained in the string $vowels. if (strpos($vowels, $letter) === false) { echo $letter; } }

Output:

cmpsr

In this case strpos($vowels, $letter) === false means that $letter is a symbol that's not a vowel letter.