In php the most commonly used string function for replacement is str_replace()
It has the following prototype:
str_replace(
array|string $search,
array|string $replace,
string|array $subject,
int &$count = null
): string|array
mixed str_replace(mixed needle, mixed new_needle, mixed haystack[, int &count]));
This function replaces all the instances of needle in haystack with new_needle and returns the new version of haystack. The optional fourth parameter, count, contains the number of replacements made.
You can pass all parameters as arrays, and the str_replace() function works remarkably intelligently. You can pass an array of words to be replaced, an array of words to replace them with (respectively), and an array of strings to apply these rules to. The function then returns an array of revised strings
Example of str_replace() function
<?php
echo str_replace("world","Peter","Hello world!");
?>
Output of str_replace() function
Hello Peter!
Example of str_replace() function
<?php
// Provides: <body text='black'>
$bodytag = str_replace("%body%", "black", "<body text='%body%'>");
// Provides: Hll Wrld f PHP
$vowels = array("a", "e", "i", "o", "u", "A", "E", "I", "O", "U");
$onlyconsonants = str_replace($vowels, "", "Hello World of PHP");
// Provides: You should eat pizza, beer, and ice cream every day
$phrase = "You should eat fruits, vegetables, and fiber every day.";
$healthy = array("fruits", "vegetables", "fiber");
$yummy = array("pizza", "beer", "ice cream");
$newphrase = str_replace($healthy, $yummy, $phrase);
// Provides: 2
$str = str_replace("ll", "", "good golly miss molly!", $count);
echo $count;
?>
More Example of str_replace example
<?php
// Order of replacement
$str = "Line 1\nLine 2\rLine 3\r\nLine 4\n";
$order = array("\r\n", "\n", "\r");
$replace = '<br />';
// Processes \r\n's first so they aren't converted twice.
$newstr = str_replace($order, $replace, $str);
// Outputs F because A is replaced with B, then B is replaced with C, and so on...
// Finally E is replaced with F, because of left to right replacements.
$search = array('A', 'B', 'C', 'D', 'E');
$replace = array('B', 'C', 'D', 'E', 'F');
$subject = 'A';
echo str_replace($search, $replace, $subject);
// Outputs: apearpearle pear
// For the same reason mentioned above
$letters = array('a', 'p');
$fruit = array('apple', 'pear');
$text = 'a p';
$output = str_replace($letters, $fruit, $text);
echo $output;
?>