Sometimes you need to ask a value: “what are you?” PHP has a family of functions for that, and each one returns true or false.
| Function | True when the value is… |
|---|---|
is_int($v) | an integer |
is_float($v) | a float |
is_string($v) | a string |
is_bool($v) | true or false |
is_array($v) | an array |
is_object($v) | an object |
is_null($v) | null |
is_numeric($v) | a number or a numeric string like "12.5" |
is_callable($v) | something that can be called as a function |
is_iterable($v) | an array or something you can loop over |
index.php
PHP
<?php
var_dump(is_int(5));
var_dump(is_int("5"));
var_dump(is_string("5"));
var_dump(is_numeric("5"));
var_dump(is_numeric("5 apples"));
var_dump(is_array([1, 2]));
Output
OUTPUT
bool(true)
bool(false)
bool(true)
bool(true)
bool(false)
bool(true)Why is_numeric() is useful
Form data always arrives as strings. is_int("25") is false, but is_numeric("25") is true, so it is the right test for typed input.
Type in a message
get_debug_type() gives a readable name that is great for error messages.
index.php
PHP
<?php
function describe(mixed $value): string
{
return "Got " . get_debug_type($value);
}
echo describe(5) . "\n";
echo describe("text") . "\n";
echo describe([1, 2]) . "\n";
echo describe(null);
Output
OUTPUT
Got int
Got string
Got array
Got nullChecking against a list of types
index.php
PHP
<?php
$value = "42";
if (is_int($value) || is_float($value)) {
echo "A real number";
} elseif (is_string($value) && is_numeric($value)) {
echo "A number written as text";
} else {
echo "Something else";
}
Output
OUTPUT
A number written as text
lightbulb
Check, then trust
Validate the type of data from outside (forms, APIs) once, close to where it enters your program. Inside your own code, type declarations do this job for you.