Opcode Descriptions and Examples
PHP Manual

DO_FCALL_BY_NAME

PHP code

<?php
/*
 * Call a function by name.  Following INIT_FCALL_BY_NAME and multiple SEND_VAL, SEND_VAR or SEND_REF.
 * opcode number: 61
 */
$x 'phpinfo';
$a $x();
?>

PHP opcodes

Function name: (null)

Compiled variables: !0=$x, !1=$a

line#op fetchextreturn operands
60 ASSIGN     !0,'phpinfo'
71 INIT_FCALL_BY_NAME     !0
 2 DO_FCALL_BY_NAME  0   
 3 ASSIGN     !1,$1
84 RETURN     1

Opcode Descriptions and Examples
PHP Manual