PHP if语句，用于检查包含数组的列中是否存在值

I have a field that stores multiple zip codes. A query result for the zip codes column may contain several zip codes: 90027,90028,90068

I need an if statement to check if a single zip code is in the result

$zipstring = $rows['pool_zip_codes']);

$zipsql = "SELECT `pool_zip_codes` FROM `cases` WHERE `id` = '{$rowid}' AND `pool_zip_codes` IN ('{$zipstring}') ";

$zipqry = mysql_query($zipsql);
$zipresult = mysql_fetch_row($zipqry);

if (($zipresult[0]) == '90068') { 
this zip code is in the list
} else {
not in list
}
};

If I read your question correctly, you want to distinguish between

#####

and

#####,#####,#####...

To do this, just use a regex to check if the field matches 5 digits.

if (preg_match("/^\d{5}$/", $zipresult[0])) {
    ...
}

Otherwise, as the others are saying, use in_array(). What they're not saying is that you'd have to explode() the string first, to make an array:

$exploded = explode(",", $zipresult[0]);

if (in_array($exploded, "99999")) {
    ....
}

EDIT per your comment you could use strpos()

$targetcode = "99999";
$found = array();
foreach ($zipresult as $row) {
    if (strpos($row['pool_zip_codes'], $targetcode) !== false) {
        $found[] = $row;
    }   
}

or in_array()

$targetcode = "99999";
$found = array();
foreach ($zipresult as $row) {
    $exploded = explode(",", $row['pool_zip_codes']);
    if (in_array($exploded, $targetcode)) {
       $found[] = $row;
    }
}

try this

$zipresult = mysql_fetch_array($zipqry);

if (($zipresult['pool_zip_codes']) == '90068') {
this zip code is in the list
} else {
not in list
}

use in_array()

as

if (in_array($zipresult[0],$zipresult)) 
{ 
echo "this zip code is in the list" ;
} 
else { 
echo "not in list"; 
} 

Split the string and use in_array:

if (in_array(explode(',', $zipresult[0]),$zipresult)) 
{ 
   #this zip code is in the list
} 
else { 
   #not in list
}