When adding colours, don't forget that PHP uses the same 'readline' as Bash does, so it has the same need to wrap all colour codes in special marker characters.
If you simply add raw colour codes to the prompt, you will notice that long lines no longer get wrapped correctly -- Readline no longer knows how wide the prompt is.
To fix this, you need to start each colour code with an '0x01' byte (aka Ctrl-A aka SOH) and end it with the '0x02' byte (aka Ctrl-B aka STX). There are no escapes for these -- you have to literally put the control characters in your php-cli.ini.
For example:
<?php
echo "cli.prompt = \x01\\e[1m\x02 PHP! \x01\\e[m\x02\n";
?>
