what's the code meaning? - php

Question

$file = fopen("test.txt","r");
while($line = fgets($file)) {
$line = trim($line);
list($model,$price) = preg_split('/\s+/',$line);
if(empty($price)) {
$price = 0;
}
$sql = "UPDATE products
SET products_price=$price
WHERE products_model='$model'";
// run the sql query.
}
fclose($file);
the txt file like this:
model price
LB2117 19.49
LB2381 25.99
1, what's the meaning of list($model,$price) = preg_split('/\s+/',$line);
i know preg_split like explode, but i don't know what't the parameter meaning of the above line
2, how to skip the first record.

Answer 1

it's taking the results of the preg_split and assigning them to the vars $model and $price. You're looking at a parsing algorithm. Sorry if this is not enough. I have a hard time understanding the question as it is written.
Also, if I read this correctly, there is no need to skip line 1 unless you have an item with the model defined as "model" in the database.
But if you wanted to for some reason, you could add a counter...
$i = 0;
while($line = fgets($file)) {
if($i > 0)
{
$line = trim($line);
list($model,$price) = preg_split('/\s+/',$line);
if(empty($price)) {
$price = 0;
}
$sql = "UPDATE products
SET products_price=$price
WHERE products_model='$model'";
// run the sql query.
}
$i++;
}

Answer 2

That is a language construct that allows you to assign to multiple variables at once. You can think of it as array unpacking (preg_split returns an array). So, when you do:
<?php
list($a, $b) = explode(".","a.b");
echo $a . "\n";
echo $b . "\n";
You will get:
a
b
Having less elements in list than the array is ok, excess elements in array are ignored, but having insufficent elements in array will give you an undefined index error. For example:
list($a) = explode(".","a.b"); // ok
list($a,$b,$c) = explode(".","a.b") // error

Answer 3

I don't know if you meant that by skip the first record but...
$file = fopen("test.txt","r"); // open file for reading
$first = true;
while($line = fgets($file)) { // get the content file
if ($first === true) { $first = false;}//skip the first record
else{
$line = trim($line); // remove the whitespace before and after the test
// not in the middle
list($model,$price) = preg_split('/\s+/',$line); // create two variable model and price, the values are from the preg_split \s means whitespace, tab and linebreak
if(empty($price)) { // if $price is empty price =0
$price = 0;
}
$sql = "UPDATE products // sql update
SET products_price=$price
WHERE products_model='$model'";
// run the sql query.
}
}
fclose($file); //close the file