Why is === faster than == in PHP?

Why is ===开发者_如何学Go faster than == in PHP?

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Because the equality operator == coerces, or converts, the data type temporarily to see if it’s equal to the other operand, whereas === (the identity operator) doesn’t need to do any converting whatsoever and thus less work is done, which makes it faster.

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=== does not perform typecasting, so 0 == '0' evaluates to true, but 0 === '0' - to false.

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There are two things to consider:

1. If operand types are different then == and === produce different results. In that case the speed of the operators does not matter; what matters is which one produces the desired result.

2. If operand types are same then you can use either == or === as both will produce same results. In that case the speed of both operators is almost identical. This is because no type conversion is performed by either operators.

I compared the speed of:

• $a == $b vs $a === $b
• where $a and $b were random integers [1, 100]
• the two variables were generated and compared one million times
• the tests were run 10 times

And here are the results:

 $a == $b $a === $b
--------- ---------
 0.765770  0.762020
 0.753041  0.825965
 0.770631  0.783696
 0.787824  0.781129
 0.757506  0.796142
 0.773537  0.796734
 0.768171  0.767894
 0.747850  0.777244
 0.836462  0.826406
 0.759361  0.773971
--------- ---------
 0.772015  0.789120

You can see that the speed is almost identical.

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First, === checks to see if the two arguments are the same type - so the number 1 and the string '1' fails on the type check before any comparisons are actually carried out. On the other hand, == doesn't check the type first and goes ahead and converts both arguments to the same type and then does the comparison.

Therefore, === is quicker at checking a fail condition

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I don't really know if it's significantly faster, but === in most languages is a direct type comparison, while == will try to do type coercion if necessary/possible to gain a match.

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The == incurs a larger overhead of type conversion before comparison. === first checks the type, then proceeds without having to do any type conversion.

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Because === doesn't need to coerce the operands to be of the same type before comparing them.

I doubt the difference in speed is very much though. Under normal circumstances you should use whichever operator makes more sense.

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In conclusion === is faster because don't converts the data type to see if two variables have same value, but when you need to see if two variables have same value you will use == if doesen't mather what type are variables, or === if is important also the type of variables.

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I found out that there actually is a significant speed difference between the 2 operators. Results for php 8.0.0 RC5 and php 7.4.12 running in docker container below. The project is hosted on github so everyone can review the methodology. Disclaimer: I built the tool.

$ php src/benchmark.php --custom --filter ~equal~
PHP benchmark

-------------------------------
platform           :  Linux x64
php version        :     7.4.12
xdebug             :        off
memory limit       :       128M
max execution      :          0
time per iteration :       50ms
iterations         :        100
-------------------------------
---------------------------------------------------
0                  :         ==       ===
mean               :     394156    459015    +16.5%
median             :     397448    461822    +16.2%
mode               :     398154    458062    +15.0%
minimum            :     313271    405692    +29.5%
maximum            :     411157    480360    +16.8%
quartile 1         :     393222    454952    +15.7%
quartile 3         :     400881    466491    +16.4%
IQ range           :       7659     11538    +50.7%
std deviation      :      15593     11867    -23.9%
normality          :       0.8%      0.8%
---------------------------------------------------

$ php src/benchmark.php --custom --filter ~equal~
PHP benchmark

-------------------------------
platform           :  Linux x64
php version        :   8.0.0RC5
xdebug             :        off
memory limit       :       128M
max execution      :          0
time per iteration :       50ms
iterations         :        100
-------------------------------
---------------------------------------------------
0                  :         ==       ===
mean               :     405032    474768    +17.2%
median             :     409226    477313    +16.6%
mode               :     408421    479741    +17.5%
minimum            :     311606    386509    +24.0%
maximum            :     417895    491842    +17.7%
quartile 1         :     405740    473436    +16.7%
quartile 3         :     412677    483139    +17.1%
IQ range           :       6937      9703    +39.9%
std deviation      :      17501     15657    -10.5%
normality          :       1.0%      1.0%
---------------------------------------------------

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Faster should not just be measured in direct execution time (direct performance tests are almost negligible in this case). That said, I would need to see a test involving iteration, or recursion, to really see if there is a significant, cumulative difference (when used in a realistic context). The testing and debugging time you will save when dealing with edge cases should be meaningful to you, also

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In php (c code) value is a "class" like:

class value
{
    $int_;
    $float_;
    $string_;
    $array_;
    $object_;
}

When your are comparing $a == $b and $a is int type, there will be something like:

if ($a->int_ == $b->int_ || $a->int_ == (int) $b->float_ || $a->int_ == (int) $b->string_ || ...)

but string '1' will not be cast to ascii code 49, it will be 1.

When you are comparing $a === $b and $a is int type, there will be someting like:

if ($a->int_ == $b->int_)

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If the test results are correct, then it must be a compiler issue,

The processor will do whatever it is told to do on a clock cycle

If it has less to do then it will be quicker to do

Addition:

Ah well actually if the compiler has already created loads of machine code to be processed, then if it has already added zillions of stuff to cope with what type of data needs comparing, then the removal of one "minor" IF will not change speeds much at all.

If anyone still reads this are then I am interesting in more discussion.

Phil