Opcode Descriptions and Examples
PHP Manual

IS_SMALLER

PHP code

<?php
/*
 * compares if value1 is less than value2
 * opcode number: 19
 */
echo (2);
?>

PHP opcodes

Function name: (null)

Compiled variables: none

line#op fetchextreturn operands
60 IS_SMALLER   ~0 1,2
 1 ECHO     ~0
72 RETURN     1

Opcode Descriptions and Examples
PHP Manual