build php Mysql query for four input variables, ignore if any variable is empty

Question

I am building an dynamic SQL Query. I have four input values which is passing from Android to PHP MySQL. The user may enter all values or leave some values empty. I want build an SQL query if the input of the any variable present. The complete SQL Query looks like

SELECT * FROM Movies WHERE `imdb_rat` IN ($val1) OR `Rotten_rate` IN ('$val2')  OR $stringgen OR `Year` IN ('$val4')

The four inputs are $val1, $val2, $stringgen & $val4.

I've tried the below steps but it's not working:

$QueryString="SELECT * FROM Moviess WHERE 1=1"; 

if (!empty($val1)) { 
$QueryString=$QueryString+" imdb_rat` IN ($val1)"; 
} 

if (!empty($val2)) { 
$QueryString=$QueryString+" `Rotten_rate` IN ($val2)"; 
} 

if (!empty($val4)) { 
$QueryString=$QueryString+" OR `Year` IN ($val4)"; 
} 

echo $QueryString;
$result = mysql_query($QueryString);

How to build SQL query when if any input is present otherwise ignore the variable in the query?

if (!empty($val4) && isset($val4)) { $QueryString=$QueryString+" OR Year IN ($val4)"; } — user5621153
– user5621153, Commented Dec 29, 2015 at 12:47
@Niyaz empty() does the same as isset() but also checks if the variable isn't empty so (!empty($val4) && isset($val4)) is like writing double code — SuperDJ
– SuperDJ, Commented Dec 29, 2015 at 14:25

SuperDJ · Accepted Answer · 2015-12-29 12:54:52Z

1

Try:

$QueryString="SELECT * FROM Moviess WHERE 1=1"; 

if (!empty($val1)) { 
$QueryString .= " imdb_rat` IN ($val1)"; 
} 

if (!empty($val2)) { 
$QueryString .= " `Rotten_rate` IN ($val2)"; 
} 

if (!empty($val4)) { 
$QueryString .= " OR `Year` IN ($val4)"; 
} 

echo $QueryString;
$result = mysql_query($QueryString);

.= is used to concatonate to the first variable mention. The use of + in a string is used in JavaScript. + in PHP would mean 1 + 1 = 2 which isn't what you want for a string.

Also note that mysql_* is deprecated and is removed in PHP7 instead use mysqli_* or PDO

answered Dec 29, 2015 at 12:54

SuperDJ

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Comments

score 1 · Accepted Answer · 2015-12-29 14:04:33Z

1

if (isset($val4) && !empty($val4)) { 
      $QueryString.=$QueryString+" OR `Year` IN ($val4)"; 
}

edited Dec 29, 2015 at 14:04

answered Dec 29, 2015 at 12:47

user5621153

1 Comment

Matt Clark Over a year ago

Hi Niyaz, it is useful to everyone if you could edit your answer to explain the why this should be used.

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