Calling POST data from a PHP file - php

Question

I have 3 php files and I want to get the month from form1.php for form3.php but the thing is, it needs to be processed in form2.php as well, how can I just get the month from form1 and display it in form3?
form1.php
<form action="form2.php" method="post">
<div class="form-title">
<p class="display-6">Salary Calculator (Part 1)</p>
</div>
<div class="form-subtitle">
<p>Employee Information</p>
</div>
<div class="form-row">
<div class="form-row-child">
<label for="inputPlaceholder4">Employee Name</label>
<select class="form-select" aria-label="Default select example" name="displayName" id="displayName">
<option selected>Select Employee</option>
<?php while($row = $result->fetch_assoc()) { ?>
<option value="<?php echo $row['displayName']; ?>"><?= $row["displayName"] ?></option>
<?php }; ?>
</select>
</div>
<div class="form-row-child">
<label for="inputPlaceholder4">Month</label>
<select class="form-select" aria-label="Default select example" name="month" id="month">
<option selected disabled>Select Month</option>
<option value="January">January</option>
<option value="Febuary">Febuary</option>
<option value="March">March</option>
<option value="April">April</option>
<option value="May">May</option>
<option value="June">June</option>
<option value="July">July</option>
<option value="August">August</option>
<option value="September">September</option>
<option value="October">October</option>
<option value="November">November</option>
<option value="December">December</option>
</select>
</div>
</div>
<div class="form-row">
<div class="form-row-child">
<input type="submit" class="btn btn-danger form1-btn" value="Proceed">
</div>
<div class="form-row-child">
</div>
</div>
</form>
form2.php
<form action="form3.php" method="post">
<div class="form-title">
<p class="display-6">Salary Calculator (Part 2)</p>
</div>
<div class="half-form">
<div class="half-form-left">
<div class="half-form-subtitle">
<p>Holidays</p>
</div>
<div class="half-form-child">
<label for="inputPlaceholder3">Regular (Per day)</label>
<select class="form-select" aria-label="Default select example" name="holidayReg" id="holidayReg">
<?php foreach ($regHolidays as $value) { ?>
<option value="<?php echo $value; ?>"><?= $value ?></option>
<?php }; ?>
</select>
</div>
<div class="half-form-child">
<label for="inputPlaceholder3">Special (Per day)</label>
<select class="form-select" aria-label="Default select example" name="holidaySpec" id="holidaySpec">
<?php foreach ($specHolidays as $value) { ?>
<option value="<?php echo $value; ?>"><?= $value ?></option>
<?php }; ?>
</select>
</div>
</div>
<div class="half-form-right">
<div class="half-form-subtitle">
<p>Overtime</p>
</div>
<div class="half-form-child">
<label for="inputPlaceholder3">Normal (Per hour)</label>
<input type="Placeholder" class="form-control" id="overtimeHoursNormal" placeholder="Placeholder" name="overtimeHoursNormal">
</div>
<div class="half-form-child">
<label for="inputPlaceholder3">Rest Day (Per hour)</label>
<input type="Placeholder" class="form-control" id="overtimeHoursSpecial" placeholder="Placeholder" name="overtimeHoursSpecial">
</div>
</div>
</div>
<div class="half-form">
<div class="half-form-left">
<div class="half-form-subtitle">
<p>Absences</p>
</div>
<div class="half-form-child">
<label for="inputPlaceholder3">Day/s absent</label>
<input type="Placeholder" class="form-control" id="absences" placeholder="Placeholder" name="absences">
</div>
</div>
<div class="half-form-right">
<input type="Placeholder" class="form-control" id="basePay" name="basePay" style="display: none;" value="<?php echo $vagueEmployee->getBasePay(); ?>">
<input type="Placeholder" class="form-control" id="workingHours" name="workingHours" style="display: none;" value="<?php echo $vagueEmployee->getWorkingHours(); ?>">
<input type="Placeholder" class="form-control" id="salaryPerHour" name="salaryPerHour" style="display: none;" value="<?php echo $salaryPerHour; ?>">
<input type="Placeholder" class="form-control" id="payFor13thMonth" name="payFor13thMonth" style="display: none;" value="<?php echo $payFor13thMonth; ?>">
</div>
</div>
<div class="form-row">
<div class="form-row-child">
<input type="submit" class="btn btn-danger form1-btn" value="Proceed">
</div>
<div class="form-row-child">
</div>
</div>
</form>
form3.php
<main class="main">
<div class="form-title">
<p class="display-6">Employee Salary</p>
</div>
<div class="">
<p>Pay after additions: Php <?php echo $payAfterAdditions; ?></p>
<p>Deductions</p>
<p>Philhealth: Php <?php echo $philhealth; ?></p>
<p>SSS: Php <?php echo $sss; ?></p>
<p>Total deductions: Php <?php echo $totalDeductions; ?></p>
<p>Taxable Salary: Php <?php echo $taxableSalary; ?></p>
<p>Final Salary: Php <?php echo $finalTax; ?></p>
<!-- lalabas lang kapag december -->
<p>13 month pay: </p>
<p> <?php echo $totalAbsences; ?></p>
<p> <?php echo $basePay; ?></p>
</div>
</main>

Answer 1

In form 2
Add the following field inside the form
<input type=hidden name=month value="<?php echo $_POST["month"]; ?>">
Then in form 3, you can use $_POST["month"] to access the month value.