PHP语句没有评估我期望的[重复]

Question

This question already has an answer here:

• Why does PHP consider 0 to be equal to a string? 8 answers

I have the following code:

<?php

$starting_id = 0;

$params = array ('val' => $starting_id);

echo parse_params ($params);

function parse_params ($params)
{
    $query = ' WHERE ';
    if ($params['val'] === NULL) {
        $query .= ' IS NULL';
        return $query;
    }
    if ($params['val'] == 'NOT NULL') {
        $query .= ' IS NOT NULL';
        return $query;
    }    
    return $query.' = '.$params['val'];
} 

When I run it, I expect to see this:

WHERE 

instead, I get the following:

WHERE IS NOT NULL

Any ideas why?

</div>

Answer 1

According to the PHP type comparison tables,

$var = 0 ; // (int)

if you compare $var == "string",

it will return true, you need to type check for this

$var === "string"

check php type comparison