Search_string:Enter the pattern of search string. This can be an array. replace_string: If search string is found then this string ( replace_string ) is to be replaced. main_string:This is our main string on which search will applied and replaced with replace string. Limit :(optional ) We can specify how many times or occurrence of search to be replaced. It can be set to -1 for unlimited search and replace. Count: ( optional )Returns the variable storing number of times search and replace is used within the string.
Example
<?Php
$string=" Welcome to plus2et.com , you can read html, php , jquery & HTML here";
$string=preg_replace("/html/","MySQL",$string);
echo $string;
?>
Output is here
Welcome to plus2et.com , you can read MySQL, php , jquery & HTML here
Note that we could change only html , not HTML . This is a case sensitive search and replace. To make it case in sensitive we have to add one i after the string delimiters.
$string=preg_replace("/html/i","MySQL",$string);
Now it is not case sensitive and both occurrence of the string HTML & html will be replaced with MySQL
Delimiters
To mark the starting and ending of the string we have used delimiters, in above case we used / as delimiters. However we can use any non-alphanumeric, non-backslash, non-whitespace character. Here is a list of commonly used delimiters to create patterns for searching.
Forward slash / , hash sign #, tildes ~
Counting Number of Replacements
We have one optional count variable which stores the number of replacements done by preg_replace().
<?Php
$string=" Welcome to plus2et.com , you can read html, php , jquery & HTML here";
$string=preg_replace("#html#i","MySQL",$string,-1,$count);
echo $string;
echo "<br>Total replacement done : $count ";
?>
Output is here
Welcome to plus2et.com , you can read MySQL, php , jquery & MySQL here
Total replacement done : 2
If you are dynamically building a query by taking different conditions connected by AND operator then this code is useful as you can replace the first occurrence of AND with a WHERE to complete your query.