John Davidson

Message:

I am trying to find an example where PHP 8.1 generates the CASE_STRICT opcode.

I found this message from @IluTov: https://chat.stackoverflow.com/transcript/message/50366061#50366061

@Derick When no jump table can be generated.

function foo($value) {

    return match ($value) {

        true => 'foo',

        null => 'bar',

    };

}

But that example only generates IS_IDENTICAL/JMPNZ/QM_ASSIGN for each case. I tried different cases and types, but only got either the regular MATCH code with jump table or the same IS_IDENTICAL/JMPNZ/QM_ASSIGN combination.

0002 T1 = IS_IDENTICAL CV0($value) bool(true)

0003 JMPNZ T1 0008

0004 T1 = IS_IDENTICAL CV0($value) null

0005 JMPNZ T1 0010

0006 JMP 0007

0007 MATCH_ERROR CV0($value)

0008 T2 = QM_ASSIGN string("foo")

0009 JMP 0012

0010 T2 = QM_ASSIGN string("bar")

0011 JMP 0012

0012 RETURN T2

What am I missing? When is CASE_STRICT generated?

---

My Answer:
CASE_STRICT opcode is generated in PHP 8.1 when a switch statement has a case with a non-constant value. This can happen when using expressions or variables as case values instead of just constants.

Here is an example where PHP 8.1 generates the CASE_STRICT opcode:

php
$var = 2;

switch ($var) {
case 1:
echo "One";
break;
case $var:
echo "Two";
break;
default:
echo "Default";
}


In this example, the second case statement uses the variable `$var` as the case value, which is a non-constant value. This will trigger the generation of the CASE_STRICT opcode in PHP 8.1.