Welcome, How to replace characters/words in a string in PHP? So, to replace the words in a string in PHP, we have an inbuilt string function in PHP. That is str_replace() function in PHP. The str_replace() function replaces some characters with some other characters in a string. This function works with the following rules: If the string to be searched is an array, it returns an array If the string to be searched is an array, find and replace is performed with every array element If both find and replace are arrays, and replace has fewer elements than find, an empty string will be used as replace If find is an array and replace is a string, the replace string will be used for every find value Note: This function is case-sensitive. Use the str_ireplace() function to perform a case-insensitive search. Note: This function is binary-safe.