从PHP中的数组中读取最长的字符串 5.3

Question

Here is part of the code.

$DatabaseArray=Array("Cooking","look","I cant","Walking the dog to the park","washing","talk","one");
  
$largest = max($DatabaseArray);
  
echo $largest. "<br />";

I would like to read the longest string from an array in PHP 5.3.0. I've tried the max function but doesnt seem to work as expected.

Answer 1

$longestEntry = array_reduce($databaseArray, function ($a, $b) { return strlen($a) > strlen($b) ? $a : $b; });

(uses PHP 5.3 syntax)

You can't just use max , since that assumes all entries are numbers. Since they're strings though, "the maximum string" could mean anything, so you have to do manual comparison using strlen . The above array_reduce method with custom reduce function does such comparison and reduces the array to the longest member.

If you have a lot of entries (and I mean a lot , hundreds or thousands and up), it may not be very efficient, since it basically applies strlen twice to the whole array. If that's a problem, this is more efficient by applying strlen only once per string:

$longestEntry = current(array_reduce($databaseArray, function ($a, $b) {
    $b = array($b, strlen($b));
    return $a[1] > $b[1] ? $a : $b;
}, array(null, 0)));

Since you're calling it a DatabaseArray though: If this is coming from the database, you should make it do the work. It's probably going to be even more efficient. Eg:

SELECT * FROM `table` ORDER BY CHAR_LENGTH(`string_col`) DESC LIMIT 1

Answer 2

$lengths = array_map('strlen', $DatabaseArray);
$maxLength = max($lengths);
$index = array_search($maxLength, $lengths);
echo $DatabaseArray[$index];

Answer 3

Like @deceze's answer, my suggestion is a single pass over the input array. @KingCrunch's has a greater cost in terms of time complexity because it is using functions to traverse the data more N times.

Below has the same fundamental logic as @deceze's PHP snippet, but uses intuitive, individual variables instead of indexed elements for temporary storage.

Code: ( Demo )

$maxLength = -1;
$longestValue = null;
foreach ($array as $value) {
    $length = strlen($value);
    if ($length > $maxLength) {
        $maxLength = $length;
        $longestValue = $value;
    }
}
var_export($longestValue);

Output:

'Walking the dog to the park'