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# PHP | stats_dens_pmf_poisson() Function

Hello folks! welcome back to a new edition of our tutorial on PHP. In this tutorial guide, we are going to be studying about the PHP stats_dens_pmf_poisson() Function.

The built-in PHP stats_dens_pmf_poisson() function is a Probability Mass Function of the poisson distribution.

## Syntax

Following below is the syntax to use this function -

`float stats_dens_pmf_poisson( float \$x,  float \$lb )`

## Parameter Details

Sr.NoParameterDescription
1

x

The value at which the probability mass is calculated.

2

lb

The parameter of the poisson distribution

## Return Value

This function returns the probability mass at x, where the random variable follows the Poisson distribution whose parameter is lb or false on failure.

## Dependencies

This built-in function was first introduced in statistics extension (PHP version 4.0.0 and PEAR v1.4.0). In this tutorial guide, we used the latest release of stats-2.0.3 (PHP v7.0.0 or newer and PEAR version 1.4.0 or newer).

### Example1

The following example below computes the probability mass at each x -

```<?php
// check for each x
foreach (range(0, 5) as \$x) {
var_dump(round(stats_dens_pmf_poisson(\$x, 1), 6));
echo "<br>";
}
?>```

#### Output

When the above code is executed, it will produce the following result -

```float(0.367879)
float(0.367879)
float(0.18394)
float(0.061313)
float(0.015328)
float(0.003066)```

### Example2

The following example below computes the probability mass for each lb -

```<?php
// check for each lb
foreach (range(0.5, 3, 0.5) as \$lb) {
var_dump(round(stats_dens_pmf_poisson(1, \$lb), 6));
echo "<br>";
}
?>```

#### Output

When the above code is executed, it will produce the following result -

```float(0.303265)
float(0.367879)
float(0.334695)
float(0.270671)
float(0.205212)
float(0.149361)```

Alright guys! This is where we are going to be rounding up for this tutorial post. In our next tutorial, we are going to be discussing about the PHP stats_dens_t() Function.

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