mixed preg_replace(mixed pattern, mixed replacement, mixed subject);
Searches subject for matches to pattern and replaces them with replacement .
replacement may contain references of the form \\n. Every such reference will be replaced by the text captured by the n'th parenthesized pattern. n can be from 0 to 99, and \\0 refers to the text matched by the whole pattern. Opening parentheses are counted from left to right (starting from 1) to obtain the number of the capturing subpattern.
If no matches are found in subject, then it will be returned unchanged.
Every parameter to preg_replace() can be an array.
If subject is an array, then the search and replace is performed on every entry of subject, and the return value is an array as well.
If pattern and replacement are arrays, then preg_replace() takes a value from each array and uses them to do search and replace on subject. If replacement has fewer values than pattern, then empty string is used for the rest of replacement values. If pattern is an array and replacement is a string; then this replacement string is used for every value of pattern. The converse would not make sense, though.
/e modifier makes preg_replace() treat the replacement parameter as PHP code after the appropriate references substitution is done. Tip: make sure that replacement constitutes a valid PHP code string, otherwise PHP will complain about a parse error at the line containing preg_replace().
Note: This modifier was added in PHP 4.0.
Example 1. Replacing several values
1 2 $startDate = 5/27/1999 3
Example 2. Using /e modifier
This would capitalize all HTML tags in the input text.