What's the maximum value for an int in PHP?

From the PHP manual:

The size of an integer is platform-dependent, although a maximum value of about two billion is the usual value (that's 32 bits signed). PHP does not support unsigned integers. Integer size can be determined using the constant PHP_INT_SIZE, and maximum value using the constant PHP_INT_MAX since PHP 4.4.0 and PHP 5.0.5.

64-bit platforms usually have a maximum value of about 9E18, except on Windows prior to PHP 7, where it was always 32 bit.

32-bit builds of PHP:

• Integers can be from -2,147,483,648 to 2,147,483,647 (~ ± 2 billion)

64-bit builds of PHP:

• Integers can be from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 (~ ± 9 quintillion)

Numbers are inclusive.

Note: some 64-bit builds once used 32-bit integers, particularly older Windows builds of PHP

Values outside of these ranges are represented by floating point values, as are non-integer values within these ranges. The interpreter will automatically determine when this switch to floating point needs to happen based on whether the result value of a calculation can't be represented as an integer.

PHP has no support for "unsigned" integers as such, limiting the maximum value of all integers to the range of a "signed" integer.