这个符号在PHP中的条件语句中意味着什么？ [重复]

Question

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• Reference — What does this symbol mean in PHP? 18 answers

Looking at the first condition //if ($_REQUEST["string"]<>''). What does <> this symbol mean? This is my first time to see one of this. Could someone explain what it is.. Thanks in advance

<?php
if ($_REQUEST["string"]<>'') {
    $search_string = " AND (full_name LIKE '%".mysql_real_escape_string($_REQUEST["string"])."%' OR email LIKE '%".mysql_real_escape_string($_REQUEST["string"])."%')"; 
}
if ($_REQUEST["city"]<>'') {
    $search_city = " AND city='".mysql_real_escape_string($_REQUEST["city"])."'";   
}

if ($_REQUEST["from"]<>'' and $_REQUEST["to"]<>'') {
    $sql = "SELECT * FROM ".$SETTINGS["data_table"]." WHERE from_date >= '".mysql_real_escape_string($_REQUEST["from"])."' AND to_date <= '".mysql_real_escape_string($_REQUEST["to"])."'".$search_string.$search_city;
} else if ($_REQUEST["from"]<>'') {
    $sql = "SELECT * FROM ".$SETTINGS["data_table"]." WHERE from_date >= '".mysql_real_escape_string($_REQUEST["from"])."'".$search_string.$search_city;
} else if ($_REQUEST["to"]<>'') {
    $sql = "SELECT * FROM ".$SETTINGS["data_table"]." WHERE to_date <= '".mysql_real_escape_string($_REQUEST["to"])."'".$search_string.$search_city;
} else {
    $sql = "SELECT * FROM ".$SETTINGS["data_table"]." WHERE id>0".$search_string.$search_city;
}

$sql_result = mysql_query ($sql, $connection ) or die ('request "Could not execute SQL query" '.$sql);
if (mysql_num_rows($sql_result)>0) {
    while ($row = mysql_fetch_assoc($sql_result)) {
?>

</div>

Answer 1

If you have google it once you'll probably get the answer comparatively then over SO

It stands for NOT EQUAL

and same as that of !=