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# readline_callback_handler_install

(PHP 5 >= 5.1.0RC1)

readline_callback_handler_install -- Initializes the readline callback interface and terminal, prints the prompt and returns immediately

## Description

bool readline_callback_handler_install ( string prompt, callback callback )

Sets up a readline callback interface then prints prompt and immediately returns. The callback function takes one parameter; the user input returned. Calling this function twice without removing the previous callback interface will automatically and conveniently overwrite the old interface.

The callback feature is useful when combined with stream_select() as it allows interleaving of IO and user input, unlike readline().

## Return Values

Returns `TRUE` on success or `FALSE` on failure.

## Examples

Example 1. Readline Callback Interface Example
`<?php function rl_callback($ret) { global $c, $prompting; echo "You entered: $ret\n"; $c++; if ($c > 10) { $prompting = false; readline_callback_handler_remove(); } else { readline_callback_handler_install("[$c] Enter something: ", 'rl_callback'); } } $c = 1; $prompting = true; readline_callback_handler_install("[$c] Enter something: ", 'rl_callback'); while ($prompting) { $n = stream_select($r = array(STDIN), $w = null, $e = null, null); if ($n && in_array(STDIN, $r)) { // read a character, will call the callback when a newline is entered readline_callback_read_char(); } } echo "Prompting disabled. All done.\n"; ?>`

## See Also

readline_callback_handler_remove(), readline_callback_read_char() and stream_select().

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