php - why the if else statement does not run the else statement? -

i have problem if , else statement in php never runs else statement.

the input form in html:

   <input type="radio" name="marital_stat" id="single" value="single" />single    <input type="radio" name="marital_stat" id="married" value="married" />married     <input name="age" type="text" size="5" maxlength="3" placeholder="30" required/>     <input name="work" type="radio" id="employee" value="employee" />employee    <input name="work" type="radio" id="own" value="own" />     own business     <input name="work" type="radio" id="jobless" value="jobless" />jobless     <input name="place" type="radio" id="urban" value="urban" />urban    <input name="place" type="radio" id="rural" value="rural" />rural</td> 

here php code:

if ($marital_stat == 'married') {     if ($age >= 18 || $age < 59)     {          if ($work == 'jobless')         {              if ($place == 'rural') { $loan_credibility == 5; }         }     } } else if ($marital_stat == 'single') {      if ($age >= 18 || $age < 59)     {         if ($work == 'employee')         {              if ($place == 'rural') { $loan_credibility == 1; }         }     } } 

here condition display output:

$a = 'positive'; $b = 'negative';  if ($loan_credibility == 5 ){     echo $b ;} else{     echo $a; } 

as see make $loan_credibility == 5; or 1; == used in equality statement checks 2 sides if equal , have use = set value, not == $loan_credibility = 5; or 1;