Is there any way to 'expect' output to error_log in PHPUnit tests?

Question

Is there any way to run a test on output created from a call to 'error_log("Message")' when doing unit tests with phpunit?

Example code, one of my functions tests a credit card with a luhn algorithm:

if($checkLuhn && ($this->_luhn_check($cardNumber) == false)) {
    error_log(__METHOD__ . " cardNumber failed luhn algorithm check.");
    return false;
}

$checkLuhn is a boolean passed in to tell it whether to do the check, the _luhn_check() returns true if the $cardNumber passes. Problem is, I have more than one test in this function that can return false. I can use assertEquals on the return value, but also want to check why the error was thrown.

Can you override error_log or otherwise grab syslog output in a unit test somehow?

Answer 1

There are a few different ways to direct where error_log() sends data.

First is to just as error_log() to send it some where else. An example would be:

error_log( 'This is a message from error_log()', 3, '/dev/stdout' );

That uses the destination option for error_log().

Another approach is to override the error_log ini setting in PHP. That would look something like:

$cur_error_log = ini_get( 'error_log' );
ini_set( 'error_log', '/dev/stdout' );
error_log( 'This is a message from error_log()' );
ini_set( 'error_log', $cur_error_log );

Of the two options I generally prefer using the destination option in error_log() when possible.

From there you could use expectOutputString() from PHPUnit to look for the data sent from error_log().