Switching from ereg to preg in PHP

You want to convert from using ereg functions to preg functions.

First, you have to add delimiters to your patterns:

For case-insensitive matching, use the /i modifier with preg_match() instead:

When using integers instead of strings as patterns or replacement values, convert the number to hexadecimal and specify it using an escape sequence:

There are a few major differences between ereg and preg. First, when you use preg functions, the pattern isn’t just the string pattern; it also needs delimiters, as in Perl, so it’s /pattern/ instead.1 So:

becomes:

When choosing your pattern delimiters, don’t put your delimiter character inside the regular expression pattern, or you’ll close the pattern early.

If you can’t find a way to avoid this problem, you need to escape any instances of your delimiters using the backslash.
Instead of doing this by hand, call addcslashes().

For example, if you use / as your delimiter:

the value of $preg_pattern is now <b>.+<\/b>.
The preg functions don’t have a parallel series of case-insensitive functions. They have a case-insensitive modifier instead. To convert, change:

to:

Adding the i after the closing delimiter makes the change. Finally, there is one last obscure difference.

If you use a number (not a string) as a pattern or replacement value in ereg_replace(), it’s assumed you are referring to the ASCII value of a character.

Therefore, because 9 is the ASCII representation of tab (i.e., \t), this code inserts tabs at the beginning of each line:

Here’s how to convert linefeed endings:

To avoid this feature in ereg functions, use this instead:

On the other hand, preg_replace() treats the number 9 as the one-character string ‘9’, not as a tab substitute. To convert these character codes for use in preg_replace(), convert them to hexadecimal and prefix them with \x.

For example, 9 becomes \x9 or \x09, and 12 becomes \x0c. Alternatively, you can use \t , \r, and \n for tabs,
carriage returns, and linefeeds, respectively.