Multiple Conditions in a while loop PHP - php

Question

What is the correct way to use boolean operators to have multiple conditions in a while loop?
I have this script here that I feel SHOULD work, however it comes up blank when I run it.
$string = '"""JOHN"" <31255555656>","DAHDI/1-1",3948723,,"",';
for ($i=0; $i<strlen($string); $i++) {
if ($string[$i] == chr(34)) {
// chr 34 is ascii value for double quote chr 44 is for comma
while (($string[$i] != chr(34)) && ($string[$i+1] != chr(44))) {
echo $string[$i];
$i++;
}
}
}
Ideally what i want is for the script to echo the the given string up until the pointer ($i) reaches a double quote and one ahead of it is a comma. I feel like this is very simple and I am clearly missing something obvious.

Answer 1

if ($string[$i] == chr(34)) {
while (($string[$i] != chr(34)) && ($string[$i+1] != chr(44)))
Your if statement will run if this character is a quote. The while statement will run for as long as this character isn't a quote (and isn't a comma)
The two are exclusive. I think you might be able to get around it by incrementing $i after the if statement, but there's almost certainly an easier way of doing this.

Answer 2

The if and the while says the opposite condition... which means the while will never have a true. I guess you wanted to check the next character ?
$string = '"""JOHN"" <31255555656>","DAHDI/1-1",3948723,,"",';
for ($i=0; $i<strlen($string); $i++)
{
if ($string[$i] == chr(34))
{
while (($string[$i+1] != chr(34)) && ($string[$i+1] != chr(44))) // notice the $i+1
// chr 34 is ascii value for double quote chr 44 is for comma
{
echo $string[$i];
$i++;
}
}
}

Answer 3

The inner loop will not end at the end of the string.
Manipulation the loop control variable ($i) inside the loop leads to difficult code.
It makes it much harder to reason about it, and check if it is correct or not.
You should avoid it.
You get a better structure if you have only one loop that move through the string one char after another. Than use a variable to remember a state, for example $inside_quotes .

Answer 4

You have a logical flaw inside your loop which will cause it to iterate over the whole string but without doing any output.
Let's say:
$a = 1;
$b = 1;
while ($a == 1)
{
while ($a != 1 && $b == 1)
{
# will never come here.
}
$a++;
}
Because $a can never be 1 and !1 at the same time the condition you have put inside each other are blocking themselves.
One common way to solve this is to tokenize the string (scan the string) and then work on the tokens:
$string = '"""JOHN"" <31255555656>","DAHDI/1-1",3948723,,"",';
$token = strtok($string, '"');
while ($token !== false)
{
$token[0] !== ',' && (print "$token\n");
$token = strtok('"');
}
This produces (Demo) the following output:
JOHN
<31255555656>
DAHDI/1-1
Which might or might not be what you are looking for. A more detailed variant of this is to have a tokenizer/scanner that has state, one that can do more (but still has the shortcoming that the escapes of the quotation marks by doubling ("") them). As this is pretty bogus, I only link it. It is bogus because:
The actual function you're looking for is called str_getcsv:
$string = '"""JOHN"" <31255555656>","DAHDI/1-1",3948723,,"",';
echo implode("\n", str_getcsv($string));
Output (Demo):
"JOHN" <31255555656>
DAHDI/1-1
3948723
If you have a whole file, take a look at the SplFileObject.

Answer 5

Since you already located the first quote with the for statement you don't need to locate the same quote again with the for statement.
remove this: (($string[$i] != chr(34)) && along with the extra ) and the code will produce the following:
"""JOHN"" <31255555656>"DAHDI/1-1"
<?php
$string = '"""JOHN"" <31255555656>","DAHDI/1-1",3948723,,"",';
for ($i=0; $i<strlen($string); $i++) {
if ($string[$i] == chr(34)) {
while ($string[$i+1] != chr(44)) {
echo $string[$i];
$i++;
}
}
}
?>