Understanding PHP intval() Function and (int) Casting

The PHP intval() function converts a mixed value to an integer. Its signature is intval(mixed $value, int $base = 10): int, where $value is the data to be converted and $base specifies the numeral system (default is decimal).

When $value is a string, intval() reads the leading numeric part until a non‑numeric character is encountered; a leading ‘-’ is recognized as a sign. If $value is a float, the function returns the truncated integer. The function returns an int and respects the platform’s integer limits (e.g., 2147483647 on 32‑bit systems).

Typical usage examples:

<?php
echo intval(42)."<br>";               // 42
echo intval(4.2)."<br>";              // 4
echo intval('42')."<br>";             // 42
echo intval('+42')."<br>";            // 42
echo intval('-42')."<br>";            // -42
echo intval(042)."<br>";              // 34 (octal)
echo intval('042')."<br>";            // 42
echo intval(1e10)."<br>";             // 1410065408
echo intval('1e10')."<br>";           // 1
echo intval(0x1A)."<br>";            // 26
echo intval(42000000)."<br>";         // 42000000
echo intval(420000000000000000000)."<br>"; // 0 (overflow)
echo intval('420000000000000000000')."<br>"; // 2147483647 (max int)
echo intval(42, 8)."<br>";            // 42 (base 8)
echo intval('42', 8)."<br>";          // 34 (octal interpretation)
echo intval(array())."<br>";          // 0
echo intval(array('foo','bar'))."<br>"; // 1
echo intval(false)."<br>";            // 0
echo intval(true)."<br>";             // 1
?>

PHP also allows casting using the (int) operator, which performs a similar conversion but is not a function call. Example casts:

<?php
echo (int)42;          // 42
echo (int)4.2;         // 4
echo (int)'42';        // 42
echo (int)'+42';       // 42
echo (int)'-42';       // -42
echo (int)042;         // 34 (octal)
echo (int)'042';       // 42
echo (int)1e10;        // 1410065408
echo (int)'1e10';      // 2147483647
echo (int)0x1A;        // 26
echo (int)42000000;    // 42000000
echo (int)420000000000000000000; // -1609564160 (overflow)
echo (int)'420000000000000000000'; // 2147483647
echo (int)array();     // 0
echo (int)array('foo','bar'); // 1
echo (int)false;       // 0
echo (int)true;        // 1
?>

Key takeaways:

The intval() function and the (int) cast produce the same results for booleans, integers, floats, strings, and arrays, staying within the maximum integer range.

When the argument is a string, intval() extracts the leading numeric portion; if the string starts with a minus sign, it is treated as a negative number.

The maximum 32‑bit signed integer value is 2147483647; values exceeding this limit are capped or wrap according to PHP’s internal handling.