Asked  1 Year ago    Answers:  5   Viewed   4 times

I want to get the first letter of a string and I've noticed that $str[0] works great. I am just not sure whether this is 'good practice', as that notation is generally used with arrays. This feature doesn't seem to be very well documented so I'm turning to you guys to tell me if it's all right – in all respects – to use this notation?

Or should I just stick to the good ol' substr($str, 0, 1)?

Also, I noted that curly braces ($str{0}) works as well. What's up with that?

 Answers

5

Yes. Strings can be seen as character arrays, and the way to access a position of an array is to use the [] operator. Usually there's no problem at all in using $str[0] (and I'm pretty sure is much faster than the substr() method).

There is only one caveat with both methods: they will get the first byte, rather than the first character. This is important if you're using multibyte encodings (such as UTF-8). If you want to support that, use mb_substr(). Arguably, you should always assume multibyte input these days, so this is the best option, but it will be slightly slower.

Saturday, June 12, 2021
 
2

OK, based on refinements to your question, what you probably want is ltrim.

$out = ltrim($in, "0");

This will strip all leading zeroes from $in. It won't remove zeroes from anywhere else, and it won't remove anything other than zeroes. Be careful; if you give it "000" you'll get back "" instead of "0".

You could use typecasting instead, as long as $in is always a number (or you want it to result in 0 if it isn't):

$out = (int) $in;
  • 007 becomes 7
  • 000 becomes 0
  • 100 stays as 100
  • 456 stays as 456
  • 00a becomes 0
  • 56a becomes 0
  • ab4 becomes 0
  • -007 becomes -7

...etc.

Now, in the unlikely event that you only want to replace the first 0, so for example "007" becomes "07", then your latest attempt mentioned in your question is almost there. You just need to add a "caret" character to make sure it only matches the start of the string:

$out = preg_replace('/^0/', '', $in);
Thursday, April 1, 2021
1

Update: I've found a better solution

I've never played with php's similar_text() function but I thought I'd give it a shot...

$array = explode(PHP_EOL,'Slim Aluminium HDMI Lead, 1m Blue
Slim Aluminium HDMI Lead, 2m Blue
Slim Aluminium HDMI Lead, 3m Blue
Frozen Kids Headphones with Volume Limiter
XLR Plug to Socket Lead, 3m
XLR Plug to Socket Lead, 6m
Monster High Kids Headphones with Volume Limiter
TMNT Kids Headphones with Volume Limiter
Batman Kids Headphones with Volume Limiter
1-Gang Cable Entry Brush Wall Plate White/White Brushes 50 x 45mm
2-Gang Cable Entry Brush Wall Plate White/White Brushes 50 x 100mm
1-Gang Cable Entry Brush Wall Plate White/Black Brushes 50 x 45mm
2-Gang Cable Entry Brush Wall Plate White/Black Brushes 50 x 100mm
Slim Aluminium HDMI Lead, 5m Blue
Slim Aluminium HDMI Lead, 7.5m Blue
6.35mm (1/4") Mono Jack to Jack Guitar Lead, 5m Orange
XLR Plug to Socket Lead, 0.5m
XLR Plug to Socket Lead, 1m
XLR Plug to Socket Lead, 2m');

$output = array();
while( empty( $array ) === false )
{
  $currentWord = array_shift( $array );
  $currentGroup = array( $currentWord );
  foreach( $array as $index => $word )
  {
    if( similar_text( $word, $currentWord, $percentage ) and $percentage > 80 )
    {
      $currentGroup[] = $word;
      unset( $array[ $index ] );
    }
  }
  $output[] = $currentGroup;
}

print_r($output);

// Array
// (
//     [0] => Array
//         (
//             [0] => Slim Aluminium HDMI Lead, 1m Blue
//             [1] => Slim Aluminium HDMI Lead, 2m Blue
//             [2] => Slim Aluminium HDMI Lead, 3m Blue
//             [3] => Slim Aluminium HDMI Lead, 5m Blue
//             [4] => Slim Aluminium HDMI Lead, 7.5m Blue
//         )
// 
//     [1] => Array
//         (
//             [0] => Frozen Kids Headphones with Volume Limiter
//             [1] => Monster High Kids Headphones with Volume Limiter
//             [2] => TMNT Kids Headphones with Volume Limiter
//             [3] => Batman Kids Headphones with Volume Limiter
//         )
// 
//     [2] => Array
//         (
//             [0] => XLR Plug to Socket Lead, 3m
//             [1] => XLR Plug to Socket Lead, 6m
//             [2] => XLR Plug to Socket Lead, 0.5m
//             [3] => XLR Plug to Socket Lead, 1m
//             [4] => XLR Plug to Socket Lead, 2m
//         )
// 
//     [3] => Array
//         (
//             [0] => 1-Gang Cable Entry Brush Wall Plate White/White Brushes 50 x 45mm
//             [1] => 2-Gang Cable Entry Brush Wall Plate White/White Brushes 50 x 100mm
//             [2] => 1-Gang Cable Entry Brush Wall Plate White/Black Brushes 50 x 45mm
//             [4] => 2-Gang Cable Entry Brush Wall Plate White/Black Brushes 50 x 100mm
//         )
// 
//     [4] => Array
//         (
//             [0] => 6.35mm (1/4") Mono Jack to Jack Guitar Lead, 5m Orange
//         )
// 
// )

Assoc array edit

$products = array(
  array('id'=>'A','name'=>'Slim Aluminium HDMI Lead, 1m Blue'),
  array('id'=>'B','name'=>'Slim Aluminium HDMI Lead, 2m Blue'),
  array('id'=>'C','name'=>'Slim Aluminium HDMI Lead, 3m Blue'),
  array('id'=>'D','name'=>'1-Gang Cable Entry Brush Wall Plate White/White Brushes 50 x 45mm'),
  array('id'=>'E','name'=>'2-Gang Cable Entry Brush Wall Plate White/White Brushes 50 x 100mm'),
  array('id'=>'F','name'=>'1-Gang Cable Entry Brush Wall Plate White/Black Brushes 50 x 45mm'),
  array('id'=>'G','name'=>'2-Gang Cable Entry Brush Wall Plate White/Black Brushes 50 x 100mm'),
  array('id'=>'H','name'=>'Slim Aluminium HDMI Lead, 5m Blue'),
  array('id'=>'I','name'=>'Slim Aluminium HDMI Lead, 7.5m Blue')
);
$output = array();
while( empty( $products) === false )
{
  $currentProduct = array_shift( $products );
  $currentGroup = array( $currentProduct );
  foreach( $products as $index => $product )
  {
    if( similar_text( $product['name'], $currentProduct['name'], $percentage ) and $percentage > 80 )
    {
      $currentGroup[] = $product;
      unset( $products[ $index ] );
    }
  }
  $output[] = $currentGroup;
}
print_r($output);
Saturday, May 29, 2021
 
MGP
 
MGP
1

See ?substring.

x <- 'hello stackoverflow'
substring(x, 1, 1)
## [1] "h"
substring(x, 2)
## [1] "ello stackoverflow"

The idea of having a pop method that both returns a value and has a side effect of updating the data stored in x is very much a concept from object-oriented programming. So rather than defining a pop function to operate on character vectors, we can make a reference class with a pop method.

PopStringFactory <- setRefClass(
  "PopString",
  fields = list(
    x = "character"  
  ),
  methods = list(
    initialize = function(x)
    {
      x <<- x
    },
    pop = function(n = 1)
    {
      if(nchar(x) == 0)
      {
        warning("Nothing to pop.")
        return("")
      }
      first <- substring(x, 1, n)
      x <<- substring(x, n + 1)
      first
    }
  )
)

x <- PopStringFactory$new("hello stackoverflow")
x
## Reference class object of class "PopString"
## Field "x":
## [1] "hello stackoverflow"
replicate(nchar(x$x), x$pop())
## [1] "h" "e" "l" "l" "o" " " "s" "t" "a" "c" "k" "o" "v" "e" "r" "f" "l" "o" "w"
Tuesday, June 1, 2021
 
Jesse
 
4

Using the in-php-array-is-the-duct-tape-of-the-universe way :P

function get_all_substrings($input, $delim = '') {
    $arr = explode($delim, $input);
    $out = array();
    for ($i = 0; $i < count($arr); $i++) {
        for ($j = $i; $j < count($arr); $j++) {
            $out[] = implode($delim, array_slice($arr, $i, $j - $i + 1));
        }       
    }
    return $out;
}

$subs = get_all_substrings("a b c", " ");
print_r($subs);
Friday, July 30, 2021
 
Marcelo
 
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