Php recursive function return null while variable have value

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This function returns NULL while $alias having value in second recursion. In first call it return the required value but when first if not matched and it recurse first the required value in avilable in $alias variable but it does not return anything.

public function checkAlias($fname='',$lname=''){

        if(!empty($fname)){
        $fname = mysql_real_escape_string($fname);
        }
        if(!empty($lname)){
        $lname = mysql_real_escape_string($lname);
        }

    $alias = strtolower($fname).strtolower($lname);
    $sql = "Select ALIAS from table where ALIAS = '$alias'";
    $query = mysql_query($sql);
    $row = mysql_fetch_row($query);
    $string_length = strlen($alias) - 1;
    $result_string = substr($alias,0,$string_length);

    if(!$row){
            print $alias;   // is printing value 
        return $alias;  // but here it returns null
    }else{
        $this->checkAlias($result_string);
        } 
    }

Answers

You forgot to return the result of the recursion call:

return $this->checkAlias($result_string);

Tuesday, October 25, 2022

joel_buursma

Is a global variable necessary? Otherwise you could simplify it this way:

function getResp($objectPassed, &$in_arr = array()) {  // <-- note the reference '&'

    foreach($objectPassed as $element) {
        if(is_object($element) || is_array($element)) { // <-- else if statement simplified
            getResp($element,$in_arr);
        } else {
            // XML is being passed, need to strip it
            $element = strip_tags($element); 

            // Trim whitespace
            $element = trim($element);

            // Push to array  
            if($element != ''  &&                      // <-- everything in one test
              !preg_match("/^[0-9]$/", $element) &&
              !in_array($element,$in_arr)) 
            {                    
                  $in_arr[] = $element;  
            } 
        }
    }
    return $in_arr;
}

Then you do:

$result = getResp($data);

If a recursive function has to access the same resource over and over again (in this case the initial array), I would always pass this as a reference.
I don't know if is measurable but I would guess that this is much more efficient than copying values.

Thursday, December 15, 2022

rusalex

You need to return the recursive function when you recurse, otherwise it will return nothing.

if($result['parent_id'] != '0') {

   return $this->Recursive($result['parent_id'],$category_array) ;

 }

Thursday, August 18, 2022

btpka3

Here's a simple algo. Iterate from 1 to 2^count(array)-1. On each iteration, if j-th bit in a binary representation of the loop counter is equal to 1, include j-th element in a combination.

As PHP needs to be able to calculate 2^count(array) as an integer, this may never exceed PHP_INT_MAX. On a 64-bit PHP installation your array cannot have more than 62 elements, as 2⁶² stays below PHP_INT_MAX while 2⁶³ exceeds it.

EDIT: This computes all possible combinations, not permutations (ie, 'abc' = 'cba'). It does so by representing the original array in binary and "counting up" from 0 to the binary representation of the full array, effectively building a list of every possible unique combination.

$a = array('a', 'b', 'c', 'd');

$len  = count($a);
$list = array();

for($i = 1; $i < (1 << $len); $i++) {
    $c = '';
    for($j = 0; $j < $len; $j++)
        if($i & (1 << $j))
            $c .= $a[$j];
    $list[] = $c;
}

print_r($list);

Tuesday, November 22, 2022

politank-z

You're not returning the text properly e.g.

    } else {
        echo 'else 1<br />';
        return $str;   <---nothing in the 'parent' caller catches this, so it's lost
    }

Anywhere you do recursion and need to return a value, you must capture/return the recursive call itself:

    return check_length(substr($str, 0, -1), $max, $size, true);

    $newstr = check_length(...);
    return $newstr;

Tuesday, November 8, 2022

abranhe

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Php recursive function return null while variable have value

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