Clever way to do for loop () ? PHP

Question

I am looking to see if there is a smart or optimal way to try and do this for loop which so far I cannot get it to work.

I am trying to do it this way to stop me repeating code however if its not possible then I will just have to repeat code.

Here is what I tried

if(!isset($staff_rows)
for ($i=0; $i < 5; $i++)
else
for ($i=0; $i < $staff_rows; $i++)

So basically I want my forloop to use a variable $staff_rows if it is set otherwise just use default value of 5.

This is the error message

Parse error : syntax error, unexpected T_FOR in

Any ideas?

Thanks

You'd missing a ). It should read if ( !isset($staff_rows) ) — Wizz, Aug 06 '11 at 15:28
Why is everyone negging this - it is a completely legit question — sqlmole, Aug 06 '11 at 15:53
That thing is called variable because you can change its value. — hakre, Aug 06 '11 at 17:32

Luigi · Answer 1 · 2011-08-06T15:35:58.587

4

$min = (isset($staff_rows)) ? $staff_rows : 5 ;
for ($i=0; $i < $min; $i++) {
  //loop logic
}

edited Aug 06 '11 at 15:35

answered Aug 06 '11 at 15:30

Luigi

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why would that error? ofcourse you have to start { and loop logic later... – Luigi Aug 06 '11 at 15:33
You're not comparing `$i` in your `for()` condition. You're merely defining and incrementing. – AlienWebguy Aug 06 '11 at 15:35

score 4 · Accepted Answer · answered Aug 06 '11 at 15:31

4

the simplest way.

        $staff_rows = 5;

        // your code to change staff_rows 

        for ($i=0; $i <  $staff_rows; $i++) {
          // do something
        }

answered Aug 06 '11 at 15:31

blejzz

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This one I have selected as the answer as it is simple in logic and is elegant! – sqlmole Aug 06 '11 at 15:53

score 1 · Answer 3 · edited May 23 '17 at 12:14

1

for($i=0,$s=(isset($staff_rows)?$staff_rows:5);$i<$s;++$i) //do

Added:
More about ternary operator:
What is ?: in PHP 5.3?

Some benchmark.Manual page in gion_13's answer

$array=range(1,1000000);
$i=17;

$start= microtime(true);
$s=sizeof($array);
for($i=0;$i<$s;++$i){
;
}
print microtime(true)-$start;
print chr(10);



$start= microtime(true);
for($i=0,$s=sizeof($array);$i<$s;++$i){
;
}
print microtime(true)-$start;
print chr(10);

$start= microtime(true);
for($i=0;$i<sizeof($array);++$i){
;
}
print microtime(true)-$start;
print chr(10);

Output

0.18430280685425
0.1843409538269
1.3922038078308

edited May 23 '17 at 12:14

Community

1
1

answered Aug 06 '11 at 15:27

RiaD

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Thanks what is the min() function? Does that select the most avaiable value? – sqlmole Aug 06 '11 at 15:28
@sqlmole, I get some mistake. You neednot min() here – RiaD Aug 06 '11 at 15:31
@AlienWebguy, it is not in condition. It will calculate 1 time. – RiaD Aug 06 '11 at 15:32
@Alien: This is good code. This calculation is computed only once. It's a know blindspot of many php developer. You should read better books or met a good CS teacher! P.S. It's not in the condition. – Micromega Aug 06 '11 at 15:32
1

@Alien haha, "for ($i=0; $i – RiaD Aug 06 '11 at 15:39
first code calc sizeof() on every iteration, but second only once, before loop, when $i=0 does – RiaD Aug 06 '11 at 15:40
Nuts, no. Blind, apparently. Commas appearing as semicolons... this is what happens when I code before breakfast! Thanks~ – AlienWebguy Aug 06 '11 at 15:48
+1 for a solid benchmark – AlienWebguy Aug 06 '11 at 15:55
1

Thanks for hijacking my question - this function is not elegant and would be hard to read if maintenance was required on a system later on but thankyou :) – sqlmole Aug 06 '11 at 15:55

Matty · Answer 4 · 2011-08-06T15:43:05.283

1

Rewrite your code to be the following:

$limit = 5;
if (isset($staff_rows)) {
    $limit = $staff_rows;
}
for ($i=0; $i < $limit; $i++) { }

Your code will also be clearer with braces. Also you were missing a closing parentheses in the code sample that was in your question.

edited Aug 06 '11 at 15:43

answered Aug 06 '11 at 15:29

Matty

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Yes but that will mean I will repeat code as I have to put all my echos in both for loops inside their braces. – sqlmole Aug 06 '11 at 15:30
This doesn't answer the OP's question at all. – AlienWebguy Aug 06 '11 at 15:31
@sqlmole If the code is identical within the respective loops, move it to a function. – Matty Aug 06 '11 at 15:32
@AlienWebguy It does now – Matty Aug 06 '11 at 15:35
I cannot have functions inside my View. I am using Codeigniter Frameworks which is MVC!! NO FUNCTIONS ALLOWED INSIDE A VIEW – sqlmole Aug 06 '11 at 15:36
@sqlmole Well, you didn't mention that restriction. – Matty Aug 06 '11 at 15:38
Well, you should have been psychic! – sqlmole Aug 06 '11 at 15:38
@sqlmole - hold on, I got a solution for you in that case – Matty Aug 06 '11 at 15:40

score 0 · Answer 5 · edited Aug 06 '11 at 15:53

0

besides the fact that you have a missing ")", you can do a single for loop:

for($i=0,$l=isset($staff_rows)?$staff_rows:5;$i<$l;$i++){
    // do your thing
}

it is efficient because you use only one for-loop.
The fact that I used logic($l=isset($staff_rows)?$staff_rows:5;) in my loop does not affect its execution... but don't take my word for it :
From the php.net docs :

for (expr1; expr2; expr3)
    statement

"The first expression (expr1) is evaluated (executed) once unconditionally at the beginning of the loop."

edited Aug 06 '11 at 15:53

AlienWebguy

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answered Aug 06 '11 at 15:31

gion_13

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@Alien if you can't understand this code, it'snot means that code is bad – RiaD Aug 06 '11 at 15:36
@Matt: Please think about what you writing first. This site is sh1t. – Micromega Aug 06 '11 at 15:44
I have not selected this function although it is clever - (a) because it does not seperate the logic of two seperate functions easily and is (b) would be very hard to debug this is there was errors in value etc – sqlmole Aug 06 '11 at 15:52

Clever way to do for loop () ? PHP

5 Answers5