Replace all occurrences of a string with str_replace()

1. str_replace
2. str_ireplace()
3. Replace with array values

str_replace()

 str_replace(
  array|string $search,
  array|string $replace,
  string|array $subject,
  int &$count = null
 ): string|array

The str_replace() function takes four arguments:

1. $search the search string (also called needle), you can use an array to search multiple keywords.
2. $replace the replacement string, you can use an array for multiple replacements.
3. $subject the string (or array) to search through.
4. $count (optional) if this argument is specified, the $count variable will be set to the number of replacements performed.

This function returns a new string (or array) with all instances of the $search string replaced with the $replace string.

Example: Replace every underscore with a space.

<?php
 $subject = 'My_website_name_is:';
 echo str_replace ('_', ' ', $subject);
 //Prints: My website name is:

Example: Delete or replace all newlines

In the following example, the first argument $search is an array containing different types of linebreak escape sequences. If either escape sequence is found in the subject string, it’s replaced by the second argument.

<?php
 $subject = 'The first line
 the second line,
 and third line.';
 $search = ["\r\n", "\r", "\n"];
 echo str_replace ($search, '', $subject);
 /*Prints:
The first line the second line, and third line.
*/

Example: Get the number of replacements performed

<?php
 $subject = 'My_website_name_is:';

 //Prints: My website name is:
 echo str_replace('_', ' ', $subject, $count) . '<br>';

 //Prints: 3
 echo $count;

The str_replace() function is case-sensitive, too perform a case-insensitive search and replace, use str_ireplace().

str_ireplace()

The str_ireplace() function works same as the str_replace() function, the only difference is that stri_replace() is not case sensitive when searching for a string.

<?php
 $str = 'Welcome to my Website';
 $search = 'my website';
 $replace = 'BrainBell.com';

 //Does not replace the string $str
 echo str_replace ($search, $replace, $str);
 //Prints: 'Welcome to Website'

 /* works, because str_ipreplace ignore the 
    case when searching*/
 echo str_ireplace ($search, $replace, $str);
 //Prints: 'Welcome to BrainBell.com'

Replace multiple strings

Another way to use str_replace() is to replace multiple strings all at the same time. The following example demonstrates how to use the str_replace() function with arrays:

<?php
 $str = 'Nos. 1. 2. 3. 4. 5.';

 $search = [1,2,3,4,5];
 $replace = ['i','ii','iii','iv','v'];
 
 echo str_replace ($search, $replace, $str, $count);
 //Prints: Nos. i. ii. iii. iv. v.

 echo $count;
 //Prints: 5

The str_replace() function matches elements of the $search array and replaces them with corresponding elements of the $replace array.

Example: Delete all unwanted characters

<?php
 $string = "To be, or not to be; that's the question?!";
 $search = ['.', ',', ':', ';', '!', '?'];
 $replace= '';
 echo str_replace($search, $replace, $string);
 //Prints: To be or not to be that's the question

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Manipulating substrings: