PHP recursive function return occurs when the desired value is not returned correctly

PHP recursive function when using return will not be able to correctly return to the desired situation, if you do not understand the reasons, it is difficult to find the wrong, the following specific examples to illustrate:

function test ($i) {    $i-=4;    if ($i <3) {        return $i;    } else{        Test ($i);}    } echo Test (30);

This code does not seem to be a problem, if you do not run the estimate you do not think he has any problems, timely operation to find that there are problems you do not necessarily know where there is a problem, but in fact, the function of the else inside is problematic. The result of executing in this code is that there is no return value.

So although the condition $i <3, return $i the entire function will not return a value. Therefore, the above PHP recursive function can be modified as follows:

function test ($i) {    $i-=4;    if ($i <3) {        return $i;    } else{        return Test ($i);//Add return, let function return value    }}echo test (30);

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