Zend PHP 7 Certification – Strings – Searching

2nd December 2017

This post covers the Searching section of the Strings chapter when studying for the Zend PHP 7 Certification.

Some of the string functions for searching characters in a given string can be seen below.

The strpos() function finds the position, starting from zero, of the first occurrence of a substring in a string. The function can take up to three parameters.

  • Haystack – The string to search in
  • Needle – The string to find
  • Offset – If specified, search will start this number of characters counted from the beginning of the string
$newstring = 'abcadef abcdef';
echo $pos = strpos($newstring, 'a'); // Outputs: 0

echo $pos = strpos($newstring, 'a', 1); // Outputs: 7

$newstring = 'abcadef abcdef';
echo $pos = strpos($newstring, 'a', 1); // Outputs: 4

As of PHP version 7.1, negative offsets have been introduced. If the value is negative, search will instead start from that many characters from the end of the string, searching backwards.

Similar to strpos(), there is stripos() which is a case-insensitive version of the function.

$newstring = 'abcdef';
$pos = strpos($newstring, 'A');
$pos2 = stripos($newstring, 'A');

var_dump($pos);
var_dump($pos2);

// Outputs:
boolean false
int 0

The strlen() function returns the length of a given string. It takes one parameter, which is the string being measured for length.

$str = 'abcdef';
echo strlen($str); // 6

$str = ' ab cd ';
echo strlen($str); // 7

Note that using strlen() on an array will return NULL and generate a warning.

The strstr() function finds the first occurrence of a string. The function takes three parameters.

  • Haystack – The input string
  • Needle – If needle is not a string, it is converted to an integer and applied as the ordinal value of a character.
  • Before Needle – If true, strstr() returns the part of the haystack before the first occurrence of the needle (excluding the needle)
$email  = 'name@example.com';
$domain = strstr($email, '@');
echo $domain; // prints @example.com

$user = strstr($email, '@', true); // As of PHP 5.3.0
echo $user; // prints name

View the other sections:

Note: This article is based on PHP version 7.1.