PHP division by 0

Divide by 0 in PHP

How the division by 0 behave in PHP8, PHP7, PHP5

PHP has evolved in the last few years. Before when dividing by 0 we only get a warning. This behaviour did not change until php8, where numeric division 10 / 0 resulted in rasing an Error DivisionByZeroError. DivisionByZeroError is thrown when an attempt is made to divide a number by zero. You have to remember that use of arithmetic operator / does not throw an exception in php7. This does not mean that they did not try to solve it in php7, they just took a different approach. In php7 intdiv() function were introduced which divide number and throws exception when dividing a number by 0. Before that php5 only warning were displayed.

Note that in php5 and below, you could write a custom function to throw an Exception when dividing by 0. Similar to intdiv(…) introduced in php7. It would not be a language build in function, but it would also solve this issue.

See demo for php8, php7, php5 (run the script)

<?php

echo "--- 2 / 0 ---". PHP_EOL;
try{
	$res = 2 / 0;
}catch(DivisionByZeroError $e){
	echo " ### Caught 2 / 0! ". $e->getMessage() . PHP_EOL;
	$res = "nothing returned - error thrown!";
}
echo "RETURNS: ";
var_dump($res);
echo " ### Continue script" . PHP_EOL;
echo PHP_EOL;

echo "--- intdiv(2, 0) ---". PHP_EOL;
try{
	$res = intdiv(2, 0);
}catch(DivisionByZeroError $e){
	echo " ### Caught intdiv(2, 0)!". $e->getMessage() . PHP_EOL;
	$res = "nothing returned - error thrown!";
}
echo "RETURNS: ";
var_dump($res);
echo " ### Continue script" . PHP_EOL;

Output – Division by 0 in PHP 8

2 / 0
### Caught 2 / 0! Division by zero
### Continue script
intdiv(2, 0)
### Caught intdiv(2, 0)! Division by zero
### Continue script

Output – Division by 0 in PHP 7

2 / 0
Warning: Division by zero in /home/user/scripts/code.php on line 5
### Continue script
intdiv(2, 0)
### Caught intdiv(2, 0)! Division by zero
### Continue script

Output – Division by 0 in PHP 5

2 / 0
Warning: Division by zero in /home/user/scripts/code.php on line 5
### Continue script
intdiv(2, 0)
Fatal error: Call to undefined function intdiv() in /home/user/scripts/code.php on line 17

<?php

/**
 * Division returns INF when dividing by 0 
 * in PHP8, PHP7, PHP5
 * 
 * @param int | float $a number to divide
 * @param int | float $b number dividing by

 * @param bool | use divint like functionality
 * 
 * @return int | float | INF
 */
function divide($a, $b, $divint = false){
    if($b == 0) return INF;
    if($divint) return ($a - $a % $b) / $b;
    return $a / $b;
}

/* Compatible with PHP8, PHP7, PHP5 */
divide(8,2); // returns int(4)
divide(8,1.1); // returns float(7.2727272727273)
divide(8,0); // returns INF

We could also use another approach such:

<?php

/**
 * Division returns INF when dividing by 0 
 * in PHP8, PHP7, PHP5
 * 
 * @param int | float $a number to divide
 * @param int | float $b number dividing by

 * @param bool | Division exluding the fraction
 * 
 * @return int | float | INF
 */
function divide($a, $b, $divint = false){
    if($b == 0) return INF;
    if($divint) return floor(($a - $a % $b) / $b);
    return $a / $b;
}

/* Compatible with PHP8, PHP7, PHP5 */
echo divide(8, 2). PHP_EOL; // returns int(4)
echo divide(8, 1.3). PHP_EOL; // returns float(7.2727272727273)
echo divide(8, 0). PHP_EOL; // returns INF