Php recursion PHPcodefunctiontest ($ a) {echo '& amp; nbsp'. $ a. '& amp; nbsp'; if ($ a & gt; 0) {php recursion problem
PHP code
function test($a) { echo ' '.$a.' '; if($a >0) { test($a-1); }else { echo '<--->'; } echo ''.$a.''; } test(3)
3 2 1 0 <---> 0 1 2 3
You can explain the operation steps, or click the reference materials for me to study, I am a newbie. Forgive me
------ Solution --------------------
Brother, a word is hard to do, call a function, you have to open up a new stack, recursive call test ($ A-1) end, has output 3 2 1 0 This understand?
Then, of course, it is <---> This is the thing, right? do you understand?
At last, we need to execute this echo to reclaim the opened stack'
'. $ .'';~~~
I don't understand where it is. I 'd like to explain it to you as much as I can ~~
------ Solution --------------------
Each layer is the same:
1. print $
2. go to the next layer for recursion or printing. <--->
3. print $
That is:
Print 3, print 2, print 1, print 0, Print <--->, print 0, print 1, print 2, print 3.
Red is Step 1, Blue is step 2.
------ Solution --------------------
Test (3) run function test:
1. echo $ a = 3 and enter if to Judge 3> 0 to execute test (2); here the function test (3) has not been completed yet. Is to execute test (2) ------- * 1;
2. test (2) echo $ a = 2 and then judge 2> 0 to execute test (1); here test (2) is not completed yet. First run test (1) ------------ * 2;
3. test (1) echo $ a = 1; then judge 1> 0 to execute test (0); here test (1) has not been completed. First run test (0) ----------- * 3;
4. test (0) echo $ a = 0; then, judge that 0> 0 has executed echo <---> echo 0;
5. 4. after the execution is complete, return to * 3. after the judgment is complete, execute echo $ a = 1;
6. after the execution is complete, return to * 2 echo $ a = 2;
7. 6. after execution, return to * 1 echo $ a = 3;
This is the depth of a layer, and then the exit of a layer.
